The present invention relates to a Stirling cycle engine for deriving mechanical or electrical output power from heat. More particularly, the present invention relates to a heat engine having a single variable volume displacement unit which performs the work of a displacement piston in causing flow of the working fluid in either direction between the hot and cold sides of the engine during the isothermal compression and expansion phases of a cycle, and also performs the work of a drive piston in driving a power output means.
One widely used configuration of the Stirling cycle engine employs two reciprocating pistons, one called a displacer piston for moving the working fluid back and forth through a regenerator, and the other called a working or power piston. These engines suffer from several disadvantages. It is difficult to synchronize the movements of the pistons and various expensive ways including the "rhombic drive" have been devised for accomplishing the synchronization mechanically. Also, the piston configuration requires the input of energy in mechanical form to drive the displacer piston. This creates sealing problems in addition to the sealing problems attendant to removing the useful output in the form of a reciprocating mechanical movement. Finally, the configuration of the prior art engines does not easily permit heat transfers over large surface areas, an obvious disadvantage when the engine is to be powered by heat derived from solar energy or other "waste" heat sources.